Soft Materials Research Articles

Bioinspired Mechanochromic Liquid Crystal Materials: From Fundamentals to Functionalities and Applications.

Inspired by intriguing color changeable ability of natural animals, the design and fabrication of artificial mechanochromic materials capable of changing colors upon stretching or pressing have attracted intense scientific interest. Liquid crystal (LC) is a self-organized soft matter with anisotropic molecular alignment. Due to the sensitivity to various external stimulations, LC has been considered as an emerging and appealing responsive building block to construct intelligent materials and advanced devices. Recently, mechanochromic LC materials have becoming a hot topic in multifields from flexible artificial skins to visualized sensors and smart biomimetic devices. In this review, the recent progress of mechanochromic LCs is comprehensively summarized. Firstly, the mechanism and functionalities of mechanochromic LC is introduced, followed by preparation of various functional materials based on mechanochromic LCs. Then the applications of mechanochromic LCs are provided. Finally, the conclusion and outlooks of this field is given. This overview is hoped to provide inspiration in fabrication of advanced functional soft materials for scientists and engineers from multidisciplines including materials science, elastomers, chemistry, and physical science.

Ferroelectric Smectic C Liquid Crystal Phase with Spontaneous Polarization in the Direction of the Director.

In the previous study, the existence of an unidentified ferroelectric smectic phase is demonstrated in the low-temperature region of the ferroelectric smectic A phase, where the layer spacing decreases with decreasing temperature. In the present study, the phase is identified by taking 2D X-ray diffraction images of a magnetically oriented sample while allowing it to rotate and constructed a 3D reciprocal space with the sample rotation angle as the third axis for the whole picture of the reciprocal lattice vectors originating from the smectic structure. Consequently, circular diffraction images are obtained when the reciprocal lattice vectors are evenly distributed on the conical surface at a certain inclination angle in the reciprocal space. This result provides clear evidence that the phase in question is smectic C. The polarization properties also showed that the observed smectic C phase has spontaneous polarization in the direction parallel to the director and is identified as ferroelectric smectic C. These results provide a new type of classification for liquid crystalline phases that has been established over many years and is a significant contribution to the basic science of soft matter research.

The Role of Bio-Inspired Soft Robotic Gloves in Stroke Rehabilitation: A Comprehensive Analytical Review

Stroke is a leading cause of long-term disability, with many survivors experiencing impaired motor function. Traditional rehabilitation methods often face limitations in achieving full functional recovery. In recent years, bio-inspired soft robotic gloves have emerged as a promising solution for enhancing stroke rehabilitation, mimicking the natural movement and adaptability of biological systems. This paper provides a comprehensive analytical review of bio-inspired soft robotic gloves designed for stroke rehabilitation, focusing on their development, fabrication methods and therapeutic applications. The primary objective of this review is to evaluate the role of bio-inspired designs in the creation of soft robotic gloves and assess their effectiveness in facilitating motor recovery post-stroke. A systematic analysis of existing literature is conducted, exploring various fabrication techniques, including soft material integration, actuators and sensors, as well as the application of these gloves in clinical and therapeutic settings. Findings from this review reveal that bio-inspired soft robotic gloves show significant potential in improving patient outcomes by enhancing finger and hand movement through assisted motor control. These devices offer advantages in terms of comfort, flexibility and adaptability, allowing for prolonged and intensive rehabilitation sessions. However, limitations remain, such as the high cost of fabrication, challenges in achieving precise motor control and the lack of large-scale clinical trials to validate long-term efficacy. The research has several implications: (1) Theoretical: advancing the understanding of bio-inspired design principles in soft robotics; (2) Methodological: highlighting fabrication techniques that enhance glove performance and user adaptability. This review offers original value by consolidating and analysing recent developments in bio-inspired soft robotic gloves, contributing to both the academic literature and practical applications in stroke rehabilitation. It emphasizes the necessity of future research to address current limitations, especially in optimizing performance and reducing production costs, while enhancing patient outcomes.

Brownian colloids in optothermal field: An experimental perspective

Colloidal matter undergoing Brownian motion serves as a model system to study various physical phenomena. Understanding the effect of external perturbation on the assembly and dynamics of “Brownian colloids” has emerged as a relevant research issue in soft matter and biological physics. Optical perturbation in the form of photonic forces and torques has added impetus to this exploration. In recent years, optothermal effects arising due to optical excitation of mesoscale matter have expanded the toolbox of light–colloidal matter interactions. In this perspective, we present an experimental viewpoint on some of the developments related to the assembly and dynamics of Brownian colloids driven by the optothermal field. Furthermore, we discuss some interesting prospects on driven colloidal matter that can have implications on soft matter physics and soft photonics.

Rapid-annealed FeSiBPCu nanocrystalline alloy with high Bs approaching 1.9 T and good bendability

To promote energy savings, high efficiency and miniaturization of power electronic devices, Fe–Si–B–P–Cu nanocrystalline soft magnetic materials with high saturation magnetization (Bs) parallel to that of the 6.5 wt% Si steel and low coercivity (Hc) are desired. In this work, 30 μm-thick Fe84Si3B10P2Cu1 and Fe84.5Si3B9.5P2Cu1 (at.%) amorphous/nanocrystalline precursor ribbons were melt-spun, which has high Fe contents comparable to that of the 6.5 wt% Si steel. These ribbons consist of an amorphous matrix and pre-existing α-Fe of approximately 28–30 nm in size possessed relatively low and similar-value activation energy of nucleation and growth in the range of 224–249 kJ/mol. Which could induce strong crystallization competition and effectively suppress coarsening of the pre-existing α-Fe. The Fe84Si3B10P2Cu1 nanocrystalline alloy obtained by rapid-annealing (∼100 °C/s) the amorphous/nanocrystalline precursor at 480 °C for 30 s (Fe84-480) exhibited a fine and uniform nanostructure containing α-Fe with small average grain size of approximately 23.1 nm and high volume fraction. The Fe84-480 alloy possessed a high Bs of approximately 1.88 T, a low Hc of 8.6 A/m, and good bendability revealed by relatively large bending fracture strain of ∼1.65%, making it a promising soft magnetic material for power electronic devices.

Phenylethynyl-Terminated Imide Oligomer-Based Thermoset Resins.

Phenylethynyl-terminated imide (PETI) oligomers are highly valued for their diverse applications in films, moldings, adhesives, and composite material matrices. PETIs can be synthesized at varying molecular weights, enabling the fine-tuning of their properties to meet specific application requirements. Upon thermal curing, these oligomers form super-rigid network structures that enhance solvent resistance, increase glass-transition temperatures, and improve elastic moduli. Their low molecular weights and melt viscosities further facilitate processing, making them particularly suitable for composites and adhesive bonding. This review examines recent advancements in developing ultra-high-temperature PETIs, focusing on their structure-processing-properties relationships. It begins with an overview of the historical background and key physicochemical characteristics of PETIs, followed by a detailed discussion of PETIs synthesized from monomers featuring noncoplanar configurations (including kink and cardo structures), fluorinated groups, flexible linkages, and liquid crystalline mesogenic structures. The review concludes by addressing current challenges in this research field and exploring potential future directions.

The Effect of Firm Size, Current Ratio, and Debt to Equity Ratio on Share Price in Food and Beverage Subsector Manufacturing Companies Listed on the Indonesia Stock Exchange

The purpose of this study is to understand how company size, liquidity, and capital structure can affect stock prices in the food and beverage industry in Indonesia, so as to provide practical guidance for stakeholders in making financial and investment decisions. This research method uses a sample of 18 manufacturing companies in the food and beverage subsector on the IDX in the 2019-2022 period. Sample selection is carried out by purposive sampling technique, which is a technique that considers and determines samples based on certain criteria. The purposive sampling technique was chosen to ensure that the samples taken are relevant and in accordance with the research objectives. The results of this study show that in the number that means that the independent variable is only able to explain the bound variable of 0.299 or 29.9%. *The Stock Price variable can be explained by 29.9% by variables such as company size, debt to equity ratio, current ratio, return on equity while the remaining 70.1% can be influenced by other factors that are not studied.

Soft Matter Electrolytes: Mechanism of Ionic Conduction Compared to Liquid or Solid Electrolytes

Soft matter electrolytes could solve the safety problem of widely used liquid electrolytes in Li-ion batteries which are burnable upon heating. Simultaneously, they could solve the problem of poor contact between electrodes and solid electrolytes. However, the ionic conductivity of soft matter electrolytes is relatively low when mechanical properties are relatively good. In the present review, mechanisms of ionic conduction in soft matter electrolytes are discussed in order to achieve higher ionic conductivity with sufficient mechanical properties where soft matter electrolytes are defined as polymer electrolytes and polymeric or inorganic gel electrolytes. They could also be defined by Young’s modulus from about Pa to Pa. Many soft matter electrolytes exhibit VFT (Vogel–Fulcher–Tammann) type temperature dependence of ionic conductivity. VFT behavior is explained by the free volume model or the configurational entropy model, which is discussed in detail. Mostly, the amorphous phase of polymer is a better ionic conductor compared to the crystalline phase. There are, however, some experimental and theoretical reports that the crystalline phase is a better ionic conductor. Some methods to increase the ionic conductivity of polymer electrolytes are discussed, such as cavitation under tensile deformation and the microporous structure of polymer electrolytes, which could be explained by the conduction mechanism of soft matter electrolytes.

Polymerization-Induced Self-Assembly Providing PEG-Gels with Dynamic Micelle-Crosslinked Hierarchical Structures and Overall Improvement of Their Comprehensive Performances.

Polymer gels are fascinating soft materials and have become excellent candidates for wearable electronics, biomedicine, sensors, etc. Synthetic gels usually suffer from poor mechanical properties, and integrating good mechanical properties, adhesiveness, stability, and self-healing performances in one gel is more difficult. Herein, polymerization-induced self-assembly (PISA) providing PEG-gels with an overall improvement in their comprehensive performances is reported. PISA synthesis is carried out in PEG (solvent) to efficiently produce various nanoparticles, which are used as the nanofillers in the subsequent synthesis of PEG-gels with dynamic micelle-crosslinked hierarchical structures. Compared to hydrogels, PEG-gels show excellent long-term stability due to the nonvolatile feature of PEG solvent. The hierarchical PEG-gels (with nanofillers) exhibit better mechanical and adhesive properties than the homogeneous-gels (without nanofillers). The energy dissipation mechanism of the PEG-gels is analyzed via stress relaxation and cyclic mechanical tests. High-density hydrogen bonds between the micelles and PAA matrix can be broken and reformed, endowing better self-healing properties of the dynamic micelle-crosslinked PEG gels. This work provides a simple strategy for producing hierarchical structural gels with enhanced properties, which offers fundamentals and inspirations for the designing of various advanced functional materials.

Investigations of strength and quality of clinched joints using digital image correlation

ABSTRACT This study examines the impact of processing conditions on joint strength and the effectiveness of digital image correlation (DIC) in detecting failure points in clinched joints. Mechanical tests, including single-lap shear and pull-out tests, were conducted using DIC to evaluate joint quality in various clinched configurations. The results showed frequent failures at the neck rejoin in clinched joints between mild steel and aluminum sheets, particularly when thinner sheets were positioned on the punch side and softer materials on the die side. DIC effectively identified defects and failure locations, offering insights into material combinations, sheet positioning, and failure modes. Although DIC was useful in detecting defects in both elastic and destructive regions, its ability to distinguish specific defect types from strain contour maps was limited. The study highlights the need for further research to extend DIC’s application to other mechanical joining systems and advocates for its proactive use in refining designs and manufacturing processes.

Effect of sub-micron deformations at opposing strain rates on the micromagnetic behaviour of non-oriented electrical steel

We are entering an era of re-electrification, seeking high-power density electrical machines with minimal resource use. Significant performance gains in electrical machines have been achieved through precise manufacturing processes, including the shaping/cutting of soft magnetic materials. However, most studies have evaluated magnetic performance at a macro level, focusing on components, while the fundamental mechanisms, e.g., how the micromagnetic behaviour is affected by mechanical interference, remain unclear. In this study, we examine the impact of sub-micron deformations at opposing strain rates (10−2 to 101 s−1) on the micromagnetic behaviour of soft magnetic non-oriented electrical steel. Using a diamond probe to indent within a single grain of polycrystalline material at different velocities, we induce quasi-static and dynamic mechanical loading. Our analysis, employing magnetic force microscopy, transmission Kikuchi diffraction, and scanning transmission electron microscopy with a pixelated detector, reveals that magnetic texture disturbances rely on the time-dependent dislocation dynamics of the Fe-BCC material. Additionally, we compress micro-pillars to further investigate these effects under bulk-isolated deformation. These findings highlight the importance of considering even ultra-small loads, such as nano-indentations and micro-pillar compressions, in the manufacturing of next-generation electric machines, as they can affect magnetic texture and performance.

Improving the thermal, mechanical, and insulating characteristics of thermal interface materials with liquid metal-based diphase structure

Improving the thermal, mechanical, and insulating characteristics of thermal interface materials with liquid metal-based diphase structure

Role of viscoelasticity in the adhesion of mushroom-shaped pillars

The contact behaviour of mushroom-shaped pillars has been extensively studied for their superior adhesive properties, often inspired by natural attachment systems observed in insects. Typically, pillars are modeled with linear elastic materials in the literature; in reality, the soft materials used for their fabrication exhibit a rate-dependent constitutive behaviour. Additionally, conventional models focus solely on the detachment phase of the pillar, overlooking the analysis of the attachment phase. As a result, they are unable to estimate the energy loss during a complete loading-unloading cycle.
This study investigates the role of viscoelasticity in the adhesion between a mushroom-shaped pillar and a rigid flat countersurface. Interactions at the interface are assumed to be governed by van der Waals forces, and the material is modeled using a standard linear solid model. Normal push and release contact cycles are simulated
at different approaching and retracting speeds.
Results reveal that, in the presence of an interfacial defect, a monotonically increasing trend in the pull-off force with pulling speed is observed. The corresponding change in the contact pressure distribution suggests a transition from short-range to long-range adhesion, corroborating recent experimental and theoretical investigations.
Moreover, the pull-off force remains invariant to the loading history due to our assumption of a flat-flat contact interface. Conversely, in the absence of defects and under the parameters used in this study, detachment occurs after reaching the theoretical contact strength, and the corresponding pull-off force is found to be rate
independent. Notably, the hysteretic loss exhibits a peak at intermediate detachment speeds, where viscous dissipation occurs, which holds true in both the presence and absence of a defect. However, the presence of a defect shifts the region where the majority of viscous dissipation takes place.

Simple and sensitive method for in vitro monitoring of red blood cell viscoelasticity by Quartz Crystal Microbalance with dissipation monitoring (QCM-D)

Viscoelasticity (VE) is the intrinsic mechano-dynamic property enabling red blood cells (RBCs) to undergo prompt and repeated deformations while maintaining structural integrity. Assessing RBC VE and how different stressors can affect it is of great interest. Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) is a technology exploiting high-frequency acoustic waves to probe soft matter rheological properties. In the present study, a QCM-D method is reported for in vitro monitoring of cell VE in viable RBCs. The method is based on casting a sensor-adherent cell monolayer and modeling it as an effective viscoelastic medium, and allows to extrapolate proxy values of both the elastic and the viscous cell shear moduli. Real-time VE changes induced by the known cell VE stressors temperature, medium tonicity, glutaraldehyde, methyl-β-cyclodextrin and cytochalasin D have been reliably identified. The method is relatively simple and inexpensive, non-invasive, and able to seize subtle changes of cell biomechanics. Hence, it could be usefully exploited for in vitro assessment of RBC rheological properties and their alterations induced by external chemico-physical stimuli.

REVIEW: Nonlinear shear rheometry: Brief history, recent progress, and challengesa)This manuscript was handled by Editorial Board Member R. H. Colby.

High-shear rate rotational rheometry provides access to the fast nonlinear dynamics of soft materials and, particularly, their shear stress (exhibiting shear thinning and/or thickening) as well as the first and second normal stress differences, along with their time-dependent behavior. These material functions are valuable for understanding a material's processing performance and constitutive behavior and, hence, for designing new materials with desired rheology. However, their accurate measurement has been one of the most formidable challenges in rheometry. Here, we provide an overview of the different approaches used, along with their merits and drawbacks, while we discuss practical guidelines for the implementation of measurement protocols. We focus on the development and use of cone-partitioned plate fixtures, which have been shown to provide reliable data over a wide range of Weissenberg numbers, when properly used. Furthermore, this review presents selected applications and results from recent developments, identifies operating measurement windows, discusses new capabilities and open problems, and, finally, it provides perspectives for further developments.

Effect of thermal shocks on the interfacial bond strength of sandwich composites built with rigid and soft materials produced through extrusion process

The mechanical behavior and adhesion strength of the sandwich composite, which consists of a flexible and a rigid material, were examined using extruded polylactic acid (PLA) and thermoplastic polyurethane (TPU). Three types of binders were combined with the appropriate hardeners to bond the extruded materials. The fabricated specimens are subjected to a different number of thermal shock cycles, with a maximum and minimum temperature of 80 °C and −18 °C, respectively. The sandwich composite's mechanical properties, including tensile, flexural, and impact strength, were assessed after 20, 40, and 80 cycles of thermal shock. The results indicated that the ductility of PLA material was significantly impacted by the thermal shock cycles. After completing the maximal thermal shock cycles, the composites joined with polyester resin exhibited a lower strength reduction in the impact specimens. Maximum tensile strength of 22.3 MPa, flexural strength of 31.6 MPa, and impact strength of 8.3 J were recorded prior to the application of thermal shocks to the specimens. The specimens that were bonded with epoxy resin recorded the maximal tensile, flexural, and impact strength. Following the thermal shock cycles, the composites bonded with epoxy resin exhibited a lesser reduction in tensile and flexural strength, while the composites bonded with polyester resin showed a lower strength reduction for impact specimens. The tensile and flexural specimens encountered a 7.54 % and 20.24 % reduction in strength, respectively, after undergoing 80 cycles of thermal shocks. The impact specimens experienced an 8.62 % reduction in strength.

Stimuli-responsive hydrogel actuators for skin therapeutics and beyond

Stimuli-responsive hydrogels are innovative soft materials that have garnered significant attention in recent years. These hydrogels can undergo phase transitions or structural changes in response to external stimuli, offering considerable potential for use as actuators. They can effectively be used for drug delivery and disease treatment by responding flexibly to a variety of stimuli. This paper first categorizes the types of external stimuli that hydrogel actuators respond to and outlines their applications in skin therapeutics. It then reviews therapeutic potentials of hydrogel actuators beyond the skin, and discusses the challenges and future prospects for the development of stimuli-responsive hydrogel actuators.

Circularly Polarized Organic Ultralong Room‐Temperature Phosphorescence: Generation, Enhancement, and Application

AbstractCircularly polarized luminescent (CPL) materials have garnered tremendous attention owing to their expanded optical properties beyond emission wavelength and intensity. Among these, the emerging circularly polarized organic ultralong room‐temperature phosphorescence (CP‐OURTP) materialsdemonstrating elegant and distinct features are of significant importance for their extended emission lifetime, which represent a novel frontier in research with promising scientific and technological applications across diverse fields. This review systematically outlines the traditional strategies to achieve CP‐OURTP including organic crystals, copolymerization, host–guest doping, a combination of the copolymerization and host–guest doping, spinning and twisting technology, and supramolecular polymer assembly. Importantly, the recent significant progress of CP‐OURTP in the chiral soft materials, such as liquid crystals (LCs) involving lyotropic LCs (cellulose nanocrystals, CNCs) and chiral thermotropic LCs (cholesteric LCs and chiral LC elastomers), is showcased. Finally, the practical applications of CP‐OURTP materials are summarized, and the review concludes with the perspectives on the current challenges and future opportunities for CP‐OURTP materials. This review aims to inspire the further innovations in the fabrication of advanced CP‐OURTP materials and enrich their promising applications.

Modular soft pneumatic actuator mimics elephant trunk locomotion

Robots support and facilitate tasks in all life fields. Soft robots specifically have the advantages of inherent compliance, safe interaction and flexible deformability. Soft pneumatic network (Pneu-Net) is a soft pneumatic actuator (SPA) composed of network of chambers that is actuated by pneumatic power. Soft Pneu-Net fits the human interface applications perfectly. In this paper, a bio-inspired modular based design for Pneu-Net actuator is developed. The actuator mimics the elephant trunk curling to be employed for rehabilitation of human hand fingers. The actuator is an integrated four Pneu-Net modules actuator which is attached to hand’s finger. The main introduced advantages in the new developed actuator are: providing four degrees of freedom (DoF) essential for finger’s motion by single compound actuator and developing a methodology for a modular soft Pneu-Net actuator that is efficiently reproducible. The actuator’s design is developed using computer aided design (CAD) software SOLIDWORKS. The design is simulated using finite element modeling (FEM) software ABAQUS. Fabrication process uses 3D printed molds. Soft material is molded in the 3D printed molds, forming actuator’s modules. Actuator’s modules are integrated by adhesion using the soft material. A proposed non-standard hyper-elastic material biaxial tension test is introduced as a quick material properties identification method that can produce a test table used for material identification in the FEM. Enhanced version for the actuator uses reinforcement fibers. Results show advances for the reinforced actuator, as it limits the unwanted actuator’s strain and deformation. The reinforced actuator shows improved energy efficiency reaches to 46%.

The Effect of Liquidity on Capital Structure with Company Size as a Moderating Variable Mediated by Profitability

This study aims to examine and analyze the effect of liquidity on capital structure, with firm size as a moderating variable and profitability as a mediating variable, conducted on companies listed in the IDX Growth 30 during the 2020-2022 period. The data used in this study are secondary data, and the sampling technique is purposive sampling. The data sources for this research come from the Indonesia Stock Exchange and the official websites of the listed companies. The results of the study show that liquidity has a negative and significant effect on capital structure, liquidity has a positive and significant effect on profitability, profitability has a negative and significant effect on capital structure, profitability is able to mediate the relationship between liquidity and capital structure, firm size is able to moderate the relationship between liquidity and capital structure, firm size is able to moderate the relationship between profitability and capital structure, and liquidity affects capital structure mediated by profitability and moderated by firm size simultaneously.